Failure Scenario
A school purchased 200 folding phone stands for student workstations. After two weeks, 37 stands had cracked near the hinge, 22 tipped backward when phones were placed upright, and 11 could no longer hold their viewing angle.
| Evidence | Observation |
|---|---|
| Material | Thin molded plastic; visible whitening near cracked hinges |
| Base | 70 mm long and 55 mm wide |
| Phone position | Phone center is approximately 40 mm behind the front edge |
| Hinge | Small pin with thin plastic surrounding it |
| User behavior | Some students adjust the angle while the phone is still on the stand |
1. Describe the Failure
Separate the visible symptoms from possible root causes.
| Symptoms: what happened? | Possible causes: why might it have happened? |
|---|---|
2. Build a Cause-and-Effect Chain
Complete at least two chains.
Cause → Immediate effect → Product failure → User impact
3. Evaluate Design Factors
- How could the material contribute to cracking?
- How could the base dimensions contribute to tipping?
- How could the hinge geometry contribute to failure?
- How might user behavior make the problem worse?
4. Redesign
Sketch an improved stand. Label at least four changes. Consider base size, material thickness, hinge support, angle adjustment, and phone placement.
5. Recommendation
Write a short engineering recommendation identifying the most likely root cause, two design changes, and one test that should be completed before producing more stands.
Submission Checklist
- All analysis questions are answered.
- Required calculations, tables, sketches, or diagrams are complete.
- The final recommendation uses evidence from the lesson.
- Your name, class period, and date are included.
Closing Reflection
What was the most important engineering or manufacturing decision you made in this lesson? Explain why it mattered.